1、TECHNICAL REPORT IECTR 62066 First edition 2002-06 Surge overvoltages and surge protection in low-voltage a.c. power systems General basic information Surtensions de choc et protection contre la foudre dans les rseaux basse tension Informations gnrales fondamentales Reference number IEC/TR 62066:200
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8、 +41 22 919 02 11 Fax: +41 22 919 03 00TECHNICAL REPORT IEC TR 62066 First edition 2002-06 Surge overvoltages and surge protection in low-voltage a.c. power systems General basic information Surtensions de choc et protection contre la foudre dans les rseaux basse tension Informations gnrales fondame
9、ntales PRICE CODE IEC 2002 Copyright - all rights reserved No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commissio
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11、ONTENTS FOREWORD.7 1 Scope.9 2 Reference documents.9 3 Definitions 10 4 Overvoltages in low-voltage systems12 5 Lightning overvoltages13 5.1 General .13 5.2 Origin of lightning surge overvoltages18 5.3 Lightning surges transferred from MV systems 21 5.4 Surges caused by direct flash to LV lines 23 5
12、5 Lightning surges induced into LV systems .23 5.6 Examples of induced overvoltages 25 5.7 Overvoltages caused by flashes to the structures or in close vicinity .27 5.8 Recapitulation on lightning overvoltages30 6 Switching overvoltages.31 6.1 General .31 6.2 Operation of circuit-breakers and switc
13、hes 35 6.3 Operation of fuses.37 6.4 Frequency of occurrence.38 6.5 Interactions with surge-protective devices .38 6.6 Recapitulation on switching overvoltages 39 7 Temporary overvoltages .40 7.1 General .40 7.2 Magnitude of temporary overvoltages due to MV and LV faults40 7.3 Temporary overvoltages
14、 due to defects in the LV electrical installation42 7.4 Probability of occurrence and severity of harm 42 7.5 Recapitulation on temporary overvoltage.44 8 System interaction overvoltages .44 8.1 General .44 8.2 Interaction between power system and communications system45 8.3 Other interactions46 8.4
15、 Recapitulation on system interactions46 9 Observations on surge overvoltages and failure rates.46 9.1 General .46 9.2 Using field failure data.47 9.3 Recapitulation of observations on failure rates 48 10 Considerations on system outage/equipment failure/fires .48 10.1 General .48 10.2 Avoiding inte
16、rference in system operation .49 10.3 Preventing permanent damage49 10.4 Costs of surge-related interruptions and failures50 10.5 Recapitulation on outages and failures52TR 62066 IEC:2002(E) 3 11 Considerations on the use of surge protection52 11.1 General .52 11.2 Power system configuration.52 11.3
17、 Types of installation 53 11.4 Occurrence of surges 53 11.5 SPD disconnector54 11.6 Risk assessment .55 11.7 Recapitulation on the need for surge protection.57 12 Surge protection application .57 12.1 General .57 12.2 Surge protective devices in power distribution systems .58 12.3 Basic system chara
18、cteristics for SPD selection59 12.4 Considerations for installation of SPDs64 12.5 Coordination among SPDs and with equipment to be protected.66 12.6 Recapitulation on surge protection application.67 Annex A (informative) Complementary information on lightning-related overvoltages 68 Annex B (inform
19、ative) Switching overvoltages.79 Annex C (informative) Complementary information on temporary overvoltages .94 Annex D (informative) Complementary information on system interaction overvoltages (see clause 8).97 Annex E (informative) Complementary information on SPD application .102 Annex F (informa
20、tive) Avoiding overvoltages through good practice for earthing and cabling124 Bibliography128 Figure 1 Examples of lightning flash coupling mechanisms 13 Figure 2 Examples of lightning flashes to a complex electrical system .15 Figure 3 Possible waveforms of lightning current striking ground-based o
21、bjects.16 Figure 4 Frequency distribution of peak currents for three types of lightning events.16 Figure 5 Map of annual thunderstorm days 7 .18 Figure 6 Direct flash to an overhead line19 Figure 7 Example of resistive coupling from lightning protection system 21 Figure 8 Typical earth coupling mech
22、anisms22 Figure 9 Typical overvoltages induced on an LV line by a near lightning flash24 Figure 10 Example of estimated frequency of occurrence of prospective induced lightning overvoltages on LV overhead lines .25 Figure 11 Model of distribution system used in the simulation26 Figure 12 Model for c
23、omputing dispersion of lightning current among parallel buildings in an example of TN-C system .28 Figure 13 Generation of overvoltage by switching an RLC circuit .31 Figure 14 Typical switching overvoltages .33 Figure 15 Example of a high-frequency switching surge.33 Figure 16 Distribution of the r
24、ate of rise of switching surges at different locations34 Figure 17 Distribution of the rise time of switching surges34 Figure 18 Rate of rise of the switching surges and their crest values .35 Figure 19 Distribution of the duration of the switching surges.35 4 TR 62066 IEC:2002(E) Figure 20 Example
25、of distribution of switching surge amplitudes measured in industrial distribution systems rated 230/400 V .36 Figure 21 Switching surge during interruption by a miniature fuse 48.38 Figure 22 Distribution of the relative frequency of occurrence of switching surges at different installations39 Figure
26、 23 PC/modem connections to the power system and to the communications system .46 Figure 24 Example of diversion of lightning current into the external services (TT system) 61 Figure 25 Considerations required for the selection of an SPD.63 Figure 26 Effect of additional connecting lead on the limit
27、ing voltage of a varistor .65 Figure 27 Basic model for energy coordination of SPDs.66 Figure A.1 Frequency distribution of the lightning peak current I max .68 Figure A.2 Frequency distribution of the total lightning charge Q total 69 Figure A.3 Frequency distribution of the transient lightning cha
28、rge Q trans .69 Figure A.4 Frequency distribution of the specific lightning energy W/R.70 Figure A.5 Frequency distribution of the maximum slope of transient current (di/dt) max 70 Figure A.6 Frequency distribution of the slope of current (di/dt) 30/90 % of negative subsequent strokes.71 Figure A.7
29、Simplified example with lightning flash to overhead LV line.71 Figure A.8 Prospective voltages between line and true earth at point of strike (node 1), at the transformer (node 2) and at the neutral conductor in the consumer installation (node 3) 72 Figure A.9 Prospective voltages relative to true e
30、arth at node 3 and at node 4 72 Figure A.10 Current to earth at the point of strike (node 1), at the transformer (node 2), and at the consumer installation (node 3) 72 Figure A.11 Distribution of overvoltage peak magnitudes recorded at the primary of an MV/LV transformer.73 Figure A.12 Circuit used
31、for the statistical computation74 Figure A.13 Comparison of measured overvoltages 51 and computed overvoltages (Anastasia)74 Figure A.14 Model for computing dispersion of lightning current among parallel buildings (TN-C system) 24.75 Figure A.15 Dispersion of lightning current among the paths define
32、d in figure A.1476 Figure A.16 Model for computing dispersion of lightning current among parallel buildings (TN-C system, Building 2 with no LPS and no SPDs at the service entrance) 24 77 Figure A.17 Currents and voltage for the example of figure A.1677 Figure B.1 Example illustrating transient reso
33、nance caused by switching.80 Figure B.2 Calculated overvoltages at the circuit nodes of figure B.1 .80 Figure B.3 Typical overvoltage occurring during capacitor bank energizing81 Figure B.4a Magnification condition .82 Figure B.4b Voltage magnification effect82 Figure B.4 Magnification of capacitor
34、switching overvoltage at remote bank.82 Figure B.5 Principle of overvoltage generated by clearing a short-circuit83 Figure B.6 Example of survey of switching overvoltages in three types of installations.85 Figure B.7 Switching surges in an industrial plant measured near the collecting bar 86 Figure
35、B.8 Frequency of occurrence at selected sites and overall results.88 Figure B.9 Test circuit and surge during trip of a miniature breaker due to inrush overload 90 Figure B.10 Example of overvoltage at the secondary collecting bar of a 230/400 V transformer substation when blowing 100 A fuses of a f
36、eeder .92TR 62066 IEC:2002(E) 5 Figure B.11 Overvoltage factor versus time duration of switching surges in a distribution system Short circuit near a feeder fuse .93 Figure B.12 Overvoltage in a distribution system depending on the cable length for different fuse ratings Short circuit at the end of
37、the cable93 Figure C.1 Temporary overvoltage resulting from a fault in the primary of the distribution transformer in a TN system according to North American practice.96 Figure D.1 PC/modem connections to the power system and communications system .98 Figure D.2 Voltage difference appearing across P
38、C/modem during surge current flow .98 Figure D.3 Voltage recorded across reference points for the PC/modem during a surge.99 Figure D.4 Insertion of a surge reference equalizer at the PC/modem ports .100 Figure D.5 Reduction of voltage difference between ports by a surge reference equalizer101 Figur
39、e E.1 Example of coordination for two voltage-limiting SPDs (MOV1 and MOV2) .103 Figure E.2 Comparison of the I/V characteristics of the two MOVs .103 Figure E.3 Current and voltage versus time characteristics for the two voltage-limiting SPDs 103 Figure E.4 Energy distribution among two voltage-lim
40、iting SPDs versus impinging current.104 Figure E.5 Idealized example for illustrating SPD coordination aspects104 Figure E.6 Calculated SPD voltages and current for a 2/20 s impulse injected in node 1.105 Figure E.7 Calculated SPD voltages and current for a 10/350 s impulse injected in node 2 106 Fi
41、gure E.8 Calculated SPD voltages and current for a 10/350 s impulse injected in node 1 107 Figure E.9 Example of coordination between a voltage-switching SPD and a voltage-limiting SPD107 Figure E.10 Current and voltage characteristics in the scheme of figure E.9 for no sparkover108 Figure E.11 Curr
42、ent and voltage characteristics in the scheme of figure E.9 with sparkover 109 Figure E.12 Voltage U SGat spark gap depending on different loads.109 Figure E.13 Coordination of two SPDs (voltage-switching type) .110 Figure E.14 Two ZnO varistors with the same nominal discharge current.111 Figure E.1
43、5 Two ZnO varistors with different nominal discharge currents.113 Figure E.16 Coordination principle for variant I 115 Figure E.17 Coordination principle for variant II .116 Figure E.18 Coordination principale for variant III 116 Figure E.19 Coordination principle for variant IV 117 Figure E.20 Let-
44、through energy method with standard pulse parameters .117 Figure E.21 Steepness factor for a surge-current waveform .120 Figure F.1 EMC cabinet protects electronic equipment against common-mode currents through cables 125 Figure F.2 Coupling of common-mode overvoltage caused by switching surges .126
45、 Figure F.3 Voltages measured in the control room on a cable shorted at the other end, at the top of the transformer. The common-mode currents are indicated for the various parallel earth conductors between A and C. 127 Table 1 Attributes and effects of lightning flashes 14 Table 2 Statistics of the
46、 significant parameters of lightning events.17 Table 3 Line-to-earth prospective overvoltage levels in the LV installation, occurrences per year 26 6 TR 62066 IEC:2002(E) Table 4 Current dispersion in available paths in the example of figure 12 (10/350 s, 100 kA)29 Table 5 Time to half-value of the
47、switching surges versus rated current of miniature fuses .37 Table 6 Maximum values of overvoltages allowed to occur during MV faults to earth .41 Table 7 Possible protection modes 64 Table B.1 Minimum, maximum and mean values of the amplitude and rate of rise of the recorded switching surges at dif
48、ferent locations 48.85 Table B.2 Distribution of recorded transients86 Table B.3 Measurement points and results of the long range measurement (second part) 1 .88 Table B.4 Amplitude and rate of rise of switching surges versus rated current of miniature circuit breakers 48.90 Table C.1 Maximum values of overvoltages allowed to occur during MV-faults to earth 94 Table C.2 Maximum possible values for TOVs in LV-installations due to LV-faults .95 Table E.1 Inductance necessary to ensure gap sparkover110 Table E.2 Normalized values .118 Table E.3 Referenc
